We propose to continue studies on the role of cyclic AMP in the action of female reproductive hormones on uterine metabolism. Much of our work will be aimed at an elucidation of the mechanism by which the steroid state of the uterus regulates the sensitivity of the uterine cyclic AMP system to catecholamines. Adenyl cyclase in extracts of hormone-treated and control uteri will be studied to determine whether the dose-response curve of catecholamines added to the extracts is shifted, i.e., are the steroids acting at the level of adenyl cyclase? Phosphodiesterase activity, in uterine extracts will be studied to determine whether steroid status of the tissue alters the activity of this enzyme. Experiments will be done to determine the earliest time after estrogen administration that enhancement of catecholamine sensitivity can be detected. Experiments will be done to determine whether the effect of beta-adrenergic agents on uterine cyclic AMP and phosphorylase is sensitive to inhibition by beta-adrenergic blocking agents in estrogen-treated versus control systems.